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UNIVERSITY  OF  ILLINOIS 

Agricultural  Experiment  Station, 


URBANA,   JULY,    1902. 


BULLETIN  NO.  75. 


STANDARDIZATION  OF  MILK  AND  CREAM. 


BY  OSCAR  ERF,  B.  Sc.,  INSTRUCTOR  IN  DAIRY  MANUFACTURES, 
COLLEGE  OF  AGRICULTURE. 


To  standardize  milk  is  to  bring1  the  butter-fat  content  to  a  given 
per  cent,  regardless  of  the  quality  of  the  milk  produced  by  the  cow. 

If  the  milk  as  drawn  from  the  cow  contains  less  butter-fat  than 
is  desired,  manifestly,  it  can  be  brought  to  the  desired  standard  by 
adding1  cream  or  extracting-  some  skim  milk. 

If,  on  the  contrary,  milk  as  yielded  by  the  cow  contains  more 
butter-fat  than  is  necessary  it  can  be  reduced  to  the  desired  stand- 
ard by  extracting-  cream  or  adding-  skim  milk. 

Both  of  these  processes  are  not  only  legitimate,  but  necessary  ; 
the  first  in  the  interest  of  the  consumer  and  the  second  in  the  in- 
terest of  the  producer,  because  the  latter  cannot  afford,  for  exam- 
ple, to  produce  milk  containing-  five  per  cent,  butter-fat  and  sell  it 
at  the  price  for  which  four  per  cent,  milk  is  sold,  any  more  than 
the  consumer  can  afford  to  pay  for  milk  containing-  five  per  cent. 

butter-fat   and  receive  milk   which    contains  only  four  per  cent 

297 


2g8  BULLETIN   NO.   75  [Jufy, 

butter-fat,  (providing-  they  are  produced  under  equal  sanitary  con- 
ditions.) 

This  increase  or  reduction  of  fat  can  be  secured  in  another  way, 
namely,  by  the  addition  of  water  ;  but  this  is  not  permissible,  for 
it  also  reduces  the  percentage  of  the  solids  not  fat ;  that  is  casein, 
milk  sugar,  and  ash  ;  whereas  standardizing  with  cream  or  skim 
milk  does  not  materially  alter  the  proportion  of  solids  other  than 
butter-fat. 

The  same  general  methods  that  will  serve  to  change  the  butter- 
fat  in  milk  to  any  desired  quantity  will  also  serve  to  produce 
cream  of  any  desired  per  cent,  of  butter-fat.  ,  The  necessity  for 
such  standardization  is  set  forth  in  Circular  51,  published  in  April, 
1902.  It  is  the  purpose  of  this  Bulletin  to  discuss  at  length  the 
practical  methods  of  standardizing. 

METHODS. 

In  standardization,  the  butter-fat  in  milk  or  cream  is  increased 
or  decreased  to  an  arbitrary  per  cent,  or  standard  which  may  be 
fixed  by  law  or  by  an  agreement  between  parties  in  which  one 
guarantees  to  furnish  the  other  a  definite  quantity  of  butter-fat  in 
every  pound  of  milk  or  cream  sold  for  a  stated  price.  This  price 
should  vary  with  the  butter-fat  in  the  milk, — the  more  butter-fat 
for  the  same  quantity  of  milk  the  higher  the  price  and  vice  versa. 
This  is  not  only  because  the  richer  milk  is  more  palatable  and 
nutritious  but  also  because  the  cost  of  production  is  greater. 

As  was  stated  before,  if  milk  contains  a  higher  per  cent,  of 
butter-fat  than  is  desired  this  fat  can  be  reduced  either  by  separat- 
ing the  cream  out  of  a  portion  of  the  milk  or  by  adding  skim  milk. 
In  case  all  the  milk  is  clarified*,  the  same  result  may  be  obtained 
by  mixing  a  less  portion  of  the  cream  with  the  skim  milk  than  was 
contained  in  the  original  milk.  Again,  there  may  be  an  instance 
in  which  no  skim  milk  is  on  hand,  but  instead  an  ample  supply  of 
milk  with  a  lower  per  cent,  of  butter-fat  than  is  desired.  This 
milk  will  answer  the  same  purpose  as  the  skim  milk,  but  a  larger 
portion  is  required  to  bring  the  per  cent,  down  to  the  proper 
standard. 

Again,  on  the  other  hand,  milk  of  a  lower  per  cent,  of  fat  than 
is  desired  may  be  standardized  by  taking  out  a  portion  of  the  skim 
milk  by  means  of  a  separator,  or  by  adding  reserved  cream ;  or,  as 


*Bythe  term  "clarified"  is  meant  milk  that  has  been  separated  for  the  purpose 
of  taking  out  some  of  the  impurities.  These  impurities  remain  in  the  separator 
bowl  and  the  cream  and  skim  milk  are  mixed  again  after  passing  through  the 
separator. 


39O2-J  STANDARDIZATION  OF  MILK  AND  CREAM.  399 

in  the  above  case,  if  the  cream  is  clarified,  by  mixing  a  greater  por- 
tion of  cream  with  skim  milk  than  there  was  in  the  original  milk. 
Here,  as  in  the  above  instance,  if  circumstances  should  arise  in 
which  there  is  no  cream  on  hand,  but  instead  milk  of  a  hig-her  per 
cent,  of  butter-fat  than  the  desired  standard  this  will  answer  the 
same  purpose  for  increasing-  the  percentag-e  of  fat  to  the  proper 
standard. 

These  changes  are  readily  effected  by  applying1  a  few  simple 
rules  in  order  to  calculate  the  quantity  of  skim  milk  to  be  added  or 
extracted  from  the  whole  milk  so  as  to  bring-  the  per  cent,  of  butter- 
fat  to  the  desired  point,  or  to  mix  milk  of  different  per  cents,  of 
butter-fat  in  such  proportions  as  to  reach  readily  the  desired  per 
cent. 

RULE  I. 

The  amount  of  skim  milk  to  be  added  or  removed  from  the 
whole  milk  to  obtain  the  desired  per  cent,  of  butter-fat  may  be  de- 
termined by  the  following-  rules: 

Multiply  the  number  of  pounds  of  milk  by  the  per  cent,  of  fat 
in  the  milk  and  the  product  will  be  the  number  of  pounds  of  but- 
ter-fat in  the  milk. 

Divide  the  number  of  pounds  of  butter-fat  in  the  milk  by  the 
•decimal  representing-  the  desired  per  cent,  of  fat,  and  the  quotient 
will  be  the  number  of  pounds  of  standardized  milk. 

Part  i .      Where  the  Percentage  of  Fat  is  too  High. 

From  the  number  of  pounds  of  standardized  milk  take  the 
number  of  pounds  of  original  milk  and  the  result  will  be  the  num- 
ber of  pounds  of  skim  milk  to  be  added  to  the  original  milk. 

To  illustrate:     1,000  pounds  of  milk  containing  4.5  per  cent,  of  butter-fat  are 
to  be  standardized  to  4  percent.;  how  many    pounds  of  milk  must  be  added? 
Since  4.5  per  cent,  equals  the  decimal  .045  then, 
iooox.045     45,  the  number  of  pounds  of   fat  in  1000  pounds  of  4.5  per  cent 

milk. 

45-;- .04=1 125,  the  number  of  pounds  of  4  per  cent,  or  standardized  milk. 
1125     1000=125,  tne  amount  of  skim  milk  to  be  added. 
To  formulate  this  problem: 
A  :  looo  :  :  4.5  :  4 
A=the  pounds  of  standardized  milk. 

1000X4.5 
B=  —  looo 

4 
B=the  number  of  pounds  of  skim  milk  to  be  added. 

Part  2.      Where  the  Percentage  of  Fat  is  too  Low. 
With  milk  that  is  to  be  standardized  from  a  lower  to  a  hig-her 
per  cent,  the  same  rule  holds  true;  but  in  this  case  take  the  num- 


300  BULLETIN   NO.   75.  [Jnfyr 

ber  of  pounds  of  standardized  milk  from  the  number  of  pounds  of 
original  milk  and  the  result  will  be  the  number  of  pounds  of  skim 
milk  to  be  removed  from  the  original  milk. 

To  illustrate:  1600  pounds  of  milk  containing  3.2  percent.  of  butter-fat  are  to 
be  standardized  to  4  per  cent.;  how  much  skim  milk  must  be  taken  from  the 
whole  milk  ? 

i6ooX.O32=5i  .2  the  number  of  pounds  of  butter-fat  in  the  origin;!  milk. 

5  1.  2  -5-.  04=  1  280,  the  number  of  pounds  of  standardized  milk. 

1600—1280=320,  the  number  of  pounds  of  skim  milk  to  be  separated  from  the 

original  milk,  or 
1600x3.2 


4 

A=the  number  of  pounds  of  standardized  milk. 
B=i6oo—  1280=320. 
B=the  number  of  pounds  of  skim  milk  to  be  removed. 

RULE  II. 

The  same  results  may  be  reached  by  the  following-  rule  which 
is  often  more  convenient  than  the  one  above  given. 

Divide  the  per  cent,  of  butter-fat  that  is  in  the  original  milk 
by  the  per  cent,  that  is  desired  in  the  standardized  milk.  The 
quotient  multiplied  by  the  given  number  of  pounds  of  milk  will  be 
the  amount  of  standardized  milk.  If  the  quantity  of  standardized 
milk  is  greater  than  the  original  amount  of  milk  the  difference 
must  be  added  in  the  form  of  skim  milk;  if  less  then  that  difference 
must  be  separated  out  as  skim  milk. 

Parti.      Where  the  Percentage  of  Fat  is  too  High. 

To  illustrate  :  200  pounds  of  milk  containing  6  per  cent,  of  fat  are  to  be 
standardized  to  4  per  cent.;  how  many  pounds  of  skim,  milk  must  be  added? 

.06-^.04=1.5.  hence  200  pounds  of  6  per  cent,  milk  must  be  increased  by  o'ne- 
half  with  skim  milk,  or  to  300  pounds.  The  difference  between  200  pounds  and 
300  pounds  is  the  amount  of  skim  milk  that  must  be  added,  or 

A=  -  —  X  200,  in  which  A=the  final  amount  of  standardized  milk. 
.04 

Part  2.      Where  the  Percentage  of  Fat  is  too  Low. 
To  illustrate  :    652  pounds  of  milk  containing  3.1  per  cent,   of  butter-fat  are 
to  be  standardized  to  4.5  per  cent.;  how  many  pounds  of  skim  milk    must   be   ex- 
tracted? 

3.  i  -T-4.5=.6oi,  or  the  fractional  part  of  652  pounds  of  3.1  per  cent,  milk  to 
which  the  amount  must  be  reduced  in  order  to  have  the  milk  contain  4.5  percent. 
butter-fat. 

652X.6oi=45o.  the  number  of  pounds  of  4.5  per  cent.  milk. 
652—450=202,  tne  number  of  pounds  of  skim  milk  to  be  removed,  or 

A==  -3—  X652,  in  which  A=the  final  amount  of  standardized  milk. 
4-5 


1QO2.]  STANDARDIZATION  OF  MILK  AND  CREAM.  30! 

RULE  III. 

Occasionally  there  may  be  a  quick  demand  for  milk  of  a  per 
cent,  of  fat  which  is  not  commonly  produced,  as  is  often  the  case 
with  city  dairy  companies.  However,  milk  of  a  known  standard 
is  always  on  hand.  In  this  case  a  definite  quantity  of  milk  is 
wanted  and  the  exact  proportions  of  milk  or  cream  to  be  added  to 
the  skim  milk  may  be  calculated  in  percentage  or  amount  as  follows: 

Divide  the  per  cent,  of  fat  in  the  milk  that  is  desired  by  the 
per  cent,  of  fat  in  the  milk  that  is  on  hand.  The  result  will  be  the 
per  cent,  of  the  milk  on  hand  to  be  taken;  the  remaining1  per  cent, 
of  milk  will  be  the  skim  milk  to  be  used. 

To  illustrate:  120  pounds  of  milk  containing  4  per  cent,  of  butter-fat  is  de- 
sired and  milk  of  6  per  cent,  fat  and  skim  milk  are  on  hand  to  be  used.  What 
per  cent,  of  the  standardized  milk  must  be  milk  with  6  per  cent,  fat  and  what  por- 
tion must  be  skim  milk;  that  is,  how  much  of  each  must  be  taken  in  order  that 
the  mixture  may  be  4  per  cent,  milk? 

.04-^.06=.  66%  or  66%  per  cent,  which  is  the  portion  of  6  per  cent,  milk  that 
the  120  pounds  of  standardized  milk  should  contain.  The  remaining  33^3  per 
cent,  must  be  skim  milk  which  it  is  necessary  to  add  to  bring  the  fat  down  to  4 
per  cent. 

66%  per  cent,  of  120  pounds=8o  pounds,  the  amount  of  6  percent,  milk  which 
must  be  mixed  with  40  pounds  of  skim  milk  to  bring  the  mixture  to  120  pounds 
of  4  per  cent.  milk. 

RULE  IV. 

Part  i.  The  actual  number  of  pounds  instead  of  the  per  cent, 
of  the  different  kinds  of  milk  to  be  added  may  be  ascertained  as  fol- 
lows : 

Multiply  the  number  of  pounds  of  standardized  milk  desired, 
by  the  per  cent,  of  butter-fat  that  the  milk  is  to  contain.  This 
gives  the  number  of  pounds  of  butter-fat  in  the  mixture.  Divide 
this  amount  by  the  per  cent,  of  butter-fat  contained  in  the  milk  on 
hand  and  the  result  will  be  the  number  of  pounds  of  that  milk 
which  the  standardized  milk  should  contain.  The  remainder 
would  be  skim  milk. 

To  illustrate:  50  pounds  of  milk  containing  3  per  cent,  fat  is  wanted,  and 
milk  containing  5  per  cent,  fat  is  to  be  used. 

50X.03  ----=1.5,  the  number  of  pounds  of  butter-fat  in  the  3  per  cent.  milk. 
1.5-^.05=30,  the  number  of  pounds  of  5  per  cent,  milk  which  the  standardized 
milk  should  contain. 
50—30^=20,  the  number  of  pounds  of  skim  milk  to  be  added. 

Part  2.  In  case  there  is  no  -whole  milk  on  hand  but  instead  skim 
milk  and  cream  of  a  known  per  cent,  of  butter- fat,  then  the  cream 
may  be  substituted  and  the  fat  reduced  to  the  desired  per  cent,  with 


302 


BULLETIN   NO.   75- 


[July, 


skim  milk.      The  proportionate  amounts  may  be  calculated  as  in  the 
tzvo  foregoing  methods. 

To  illustrate:  To  make  50  pounds  of  milk  containing  3  per  cent,  of  fat  or  1.5, 
pounds  of  butter-fat  as  in  the  above  illustration.  If  25  per  cent,  cream  is  to  be 
substituted  for  5  per  cent,  milk  then  the  standardized  milk  would  have  to  contain 
6  pounds  of  25  per  cent,  cream  and  44  pounds  of  skim  milk. 

As  a  matter  of  convenience  the  results  of  the  above  rules  cal- 
culated on  the  per  cent,  or  100  pound  basis  can  be  tabulated  in 
such  a  manner  as  to  reduce  the  calculation  to  a  minimum. 

TABLE  1  INDICATES  QUANTITY  OF  SKIM  MILK  TO,  BE  ADDED  TO  OR 

SUBTRACTED  FROM  100  POUNDS  OF  MILK  TO  MAKE  THE 

DESIRED  PER  CENT. 


*A 

3-25 

3-50 

3-75 

4.0 

4.25 

4.50 

4-75 

5.0 

3- 

-  7-693 

-14.285 

—  20.000 

—  25.000 

-29.412 

-33-333 

-36.842 

—  40.000 

-  4.616 

—  11.428 

-17-333 

—  22.50 

-27.059 

-31.111 

-34-737 

—38.000 

3-2 

-  1-539 

-  8.571 

-14.666 

—20.000 

—  24.706 

-28.888 

-32.632 

—36.000 

3-3 

+  1-539 

-  5.7I4 

—  I2.OOO 

-17.50 

-22.353 

-26.666 

-30  527 

-34.000 

3-4 

f  4.6r6 

-  2.857 

-  9-333 

—  15.00 

—  20.000 

-24-444 

—28.422 

—  32.000 

3-5 

f-  7-693 

—    O.OOO 

-  6.666 

—  12.50 

-17.647 

—  22.222 

-26.317 

—30.000 

3-6 

+  10.760 

+  2.857 

-  4.000 

—  IO.OO 

-15.294 

—  2O.OOO 

—24.212 

—  28.000 

'  3-7 

+13-837 

h  5-714 

-  i,333 

-  7-50 

-12.941 

-17.777 

-22.107 

—  26.000 

3-8 

+  16.914 

1-  8.571 

+  1-333 

—  5.00 

-10588 

-15-555 

—  20.000 

—  24.000 

3-9 

+  19.091 

+  11.428 

+  4.000 

—  2.50 

-    8.235 

-13-333 

-  17-897 

—  22.000 

4-0 

+23.068 

+  14-285 

+  6.666 

—  o.oo 

-    5.882 

—  II.  Ill 

-I5-792 

—  20.0OO 

4-1 

+26.145 

+17.142 

+  9-333 

+  2.50 

-    2.429 

-  8.888 

-13-687 

—  iS.OOO 

4-2 

+29.222 

+19.999 

+  12.000 

+  5-°o 

—    0.076 

-  6.666 

-11.582 

—  I6.OOO 

4-3 

+32.299 

+22856 

+  14.666 

+  7-50 

+   0.076 

-  4-444 

-  9-477 

—  14.000 

4-4 

+35-376 

+25-713 

+  17-333 

+  1  O.OO 

f   2.429 

—    2.222 

-  7-372 

—  I2.00O 

4-5 

+38-453 

+28.57 

+2O.OOO 

+12.50 

+    5.882 

—    O.OOO 

-  5-267 

—  I  O.OOO 

4.6 

+41.530 

+31-427 

+22.666 

+15.00 

+  8.235 

+    2.222 

-  3-162 

—    8.OOO 

4-7 

+44.607 

+34-284 

+25-333 

+17.50 

+  10.588 

+  4-444 

-   1.057 

—  6.000 

4.8 

+  47.684 

+37-I4I 

+28.000 

+20.00 

+  12.941 

+  6.666 

+  1-057 

-  4.000 

4-9 

+50.761 

+39.998 

+30.666 

+22.50 

+  17.647 

+  8.888    +  3.162 

—    2.OOO 

.  5-0 

53.838 

42.855 

33-333 

25.000 

20.000 

ii.  in  '  +  5.267 

—    0.000 

To  find  the  pounds  of  skim  milk  to  be  added  or  removed  trace 
the  vertical  column  of  the  per  cent,  of  fat  you  desire  down  to  where 
the  horizontal  column  representing-  the  per  cent,  of  fat  in  the  milk 
on  hand  intersects  and  the  result  will  be  the  number  of  pounds  of 
skim  milk  to  be  added  or  removed,  as  indicated  by  a  plus  or  minus 
sign  before  the  result. 

To  illustrate:  If  milk  containing  4.5  per  cent,  is  desired  and  milk  containing 
3.8  per  cent,  fat  is  on  hand,  then  15.5  pounds  for  every  hundred  pounds  or  15.5 
per  cent,  of  the  quantity  must  be  separated  out  as  skim  milk. 


*Top  line  A  represents  the  per  cent,  of  fat  that  is  desired  in  milk. 
tLeft  hand  column  B  represents  the  per  cent,  of  fat  in  milk  on  hand. 


l()O2.]  STANDARDIZATION  OF  MILK  AND  CREAM.  303 

To  STANDARDIZE  WITH  WHOLE  MILK  OR  CREAM  INSTEAD  OF  SKIM 

MILK. 

RULE  V. 

Part  i.  An  instance  may  occur  in  which  milk  is  to  be  raised  to 
a  higher  per  cent,  -with  milk  of  a  still  higher  per  cent,  of  butter- fat. 
The  quantity  to  be  added  may  be  found  in  the  following  manner. 

From  the  desired  per  cent,  of  fat  in  the  standardized  milk  sub- 
tract the  per  cent,  of  fat  in  the  milk  that  is  on  hand  which  con- 
tains the  lower  per  cent,  of  fat.  Subtract  the  per  cent,  of  fat  that 
is  desired  in  milk  from  the  per  cent,  of  fat  in  the  milk  that  is  on 
hand  which  contains  a  hig-her  per  cent,  of  butter-fat.  Divide  the 
difference  between  the  lower  per  cent,  and  the  per  cent,  desired  by 
the  difference  between  the  hig-her  per  cent,  and  the  per  cent,  de- 
sired. The  quotient  will  be  that  part  of  any  given  quantity  of 
milk  containing-  the  hig-her  per  cent,  that  should  be  taken.  Mul- 
tiply the  quotient  by  the  quantity  of  milk  of  the  lower  per  cent, 
this  will  equal  the  quantity  of  milk  of  the  hig-her  per  cent,  to  be 
added  to  the  milk  of  the  lower  per  cent,  and  the  sum  will  equal 
the  amount  of  the  mixture  containing-  the  desired  per  cent. 

To  illustrate:  Standardize  200  pounds  of  milk  containing  3  per  cent,  butter- 
fat  to  4  per  cent,  fat  with  5.2  per  cent,  milk;  how  many  pounds  of  the  latter  must 
be  added  to  bring  the  fat  up  to  4  per  cent.? 

.04— x>3=.oi. 

.052  — .O4  =  .OI2. 

.o  i  -4-  .01 2 =.833. 

200 X. 833=  1 66.6,  the  number  of  pounds  of  5.2  per  cent,  milk  to  be  added. 

200+166.6=366.6,  the  number  of  pounds  of  4  per  cent,  milk  to  be  used. 

Part  2.  To  standardize  milk  of  a  higher  per  cent,  than  is  de- 
sired with  milk  of  a  lower  per  cent,  of  fat,  the  same  rule  applies 
except  that  the  difference  between  the  desired  per  cent,  and  the  higher 
per  cent,  must  be  divided  by  the  difference  between  the  desired  per 
cent,  and  the  lower  per  cent,  of  butter- fat. 

To  illustrate:  54  pounds  of  milk  containing  5.3  per  cent,  of  butter-fat  are  to 
be  standardized  to  4  per  cent,  with  milk  containing  3.1  per  cent,  butter-fat;  how 
many  pounds  of  the  3.1  per  cent,  milk  will  be  required? 

.053— .04=. 01 3 

.04 — .03 1  =  .009 

.01 3 -=-.009  =1.44 

54X1.44  =  77.76,  the  number  of  pounds  of  milk  containing  3.1  per  cent,  of  fat 
to  be  added  to  the  54  pounds  to  decrease  the  fat  content  to  4  per  cent. 


BULLETIN   NO.   75. 


[July, 


RULE  VI. 

\ 

To  Find  the  Ratio  of  the  Number  of  Pounds  of  Milk  of  the  Different 

Per   Cents. 

Subtract  the  per  cent,  of  fat  in  the  milk  of  the  lower  fat  con- 
tent from  the  per  cent,  of  fat  desired  in  the  standardized  milk  and 
divide  this  result  by  the  difference  between  the  fat  per  cents,  in 
the  milk  of  the  higher  fat  content  and  the  lower  fat  content,  the 
quotient  represents  the  per  cent,  of  milk  of  the  higher  fat  content 
to  be  used  in  standardizing. 

To  illustrate:  Find  the  ratio  of  the  pounds  of  milk  for  mixing  5  with  3.5  to 
give  4  per  cent.  milk. 

4— 3-5=-5 

5-3-5  =  1-5 

.5-^-1. 5=.33K  °r  33/4  Per  cent,  which  is  that  part  of  the  standardized  milk 
containing  5  per  cent,  which  is  used  in  mixing  with  milk  of  3.5  per  cent,  fat  con- 
tent. Supposing  400  pounds  of  milk  of  4  per  cent  butter-fat  is  desired  then  33*4 
per  cent,  of  the  400  pounds  or  133.3  pounds  are  to  be  milk  containing  5  per  cent, 
butter-fat  and  400 — 133.3  —  266.6,  the  number  of  pounds  of  milk  of  3.5  per  cent, 
butter-fat  that  are  to  be  taken  to  bring  the  fat  content  to  4  per  cent. 

Where  whole  milk  is  used  for  standardizing  the  results  can  be 
tabulated  equally  as  well  as  when  skim  milk  is  used.  In  this  case 
the  whole  milk  has  a  constant  per  cent,  in  each  table. 

TABLE  2.     To  STANDARDIZE  CREAM  WITH  MILK  CONTAINING  '4 
PER  CENT.  OF  BUTTER-FAT. 


*A 

17 

20 

22 

25 

27 

30 

tB 

18 

92.857 

19 

86.666 

20 

81  .250 

ICO. 

21 

76.4706 

94.706 

22 

72.2222 

88.8888 

IOO. 



23 

68.4222 

84.2222 

94.212=; 

24 

65  .0000 

80.0000 

90.0000 

25 

61  .QOI; 

76  loot; 

8;  7143 

IOO. 

76 

59.0909 

72.7272 

81.8181 

95.4545 

.  ... 

27 

56.5217 

69.  s6u 

78.2608 

91  .3044 

IOO. 

28 

54.1666 

66.6666 

75.0000 

87.5000 

95.8333 

29 

52.0000 

64  .  oooo 

72.0000 

84.0000 

92.0000 

3° 

50  .  oooo 

61.5385 

69  .  2308 

80.3461 

88.4615 

lOO.OO 

*A  represents  the  per  cent,  of  fat  that  is  desired  in  cream. 

fLeft  hand  column  B  represents  the  per  cent,  of  fat  in  cream  on  hand. 

If  cream  is  to  be  standardized  with  whole  milk  the  result 
found  by  the  intersecting  columns  represents  the  pounds  per  hun- 
dred or  the  per  cent,  of  the  quantity  which  is  cream  of  the  per  cent, 
of  fat  on  hand. 


IQO2.]  STANDARDIZATION  OF  MILK  AND  CREAM.  305 


To  illustrate:  If  cream  containing  20  per  cent,  of  butter-fat  is  desired  and 
cream  containing  26  per  cent,  of  butter-fat  is  on  hand  then  72.7  per  cent,  of  the 
quantity  desired  must  be  cream  containing  26  per  cent,  of  butter-fat  and  27.3  per 
cent,  of  the  quantity  must  be  4  per  cent.  milk. 

STANDARDIZATION  OF  CREAM. 

As  stated  above,  the  principal  difference  between  milk  and 
cream  is  that  in  cream  a  larger  portion  of  the  water  is  displaced 
with  butter-fat  and  since  the  variations  lie  mainly  between  the 
butter-fat  and  the  water  the  same  methods  that  apply  to  the  stan- 
dardization of  milk  will  apply  to  the  standardization  of  cream. 

APPARATUS. 

The  apparatus  that  is  required  for  standardizing-  milk  or 
cream  is  a  creamer,  or  much  better  a  cream  separator,  a  Babcock 
tester,  scales,  and  a  mixing  vat. 

It  requires  considerable  time  to  raise  cream  with  a  creamer 
and  on  account  of  this,  cream  that  is  produced  by  this  method  in- 
variably has  an  increased  number  of  bacteria  which  when  mixed 
with  fresh  milk  is  apt  to  lessen  the  keeping  quality  of  the  stan- 
dardized milk.  It  is,  therefore,  far  more  desirable  and  also  more 
practical  to  use  the  cream  separator  and  since  this  machine  is  used 
by  many  of  the  large  distributing  concerns  for  clarifying  milk,  it 
at  the  same  time  answers  for  standardizing.  Another  advantage 
is  that  a  portion  of  the  milk  can  be  readily  separated  and  the 
cream  and  skim  milk  mixed  again  in  the  proper  proportions  with- 
out delaying  the  delivery  of  the  milk.  Since  mixing  old  cream 
with  the  fresh  milk  has  a  tendency  to  increase  the  fermentation, 
the  cream  separator  should  certainly  supersede  the  old  creamer  for 
standardization. 

Nearly  every  cream  separator  has  some  contrivance  by  which 
the  richness  of  the  cream  can  be  regulated  but  these  regulations 
are  far  from  accurate.  A  fairly  uniform  cream  delivered  by  the 
separator  in  daily  operation  may  have  a  range  of  variations  of  five 
per  cent,  above  or  below  the  per  cent,  desired.  These  variations 
even  in  a  minimum  case  would  result  in  great  profit  or  loss,  as  the 
case  may  be,  too  great  for  a  healthy  legitimate  business.  To  il- 
lustrate: Take  50  gallons  of  cream  containing  20  per  cent,  of 
butter-fat  and  as  a  variation,  let  there  be  5  per  cent,  more  butter- 
fat  than  the  standard  requires.  Assume  that  the  cream  is  sold  at 
an  average  price  of  80  cents  a  gallon.  The  loss  to  the  party  sell- 
ing the  cream  would  amount  to  $10.00,  on  the  50  gallons,  which 


306  BULLETIN   NO.   7$.  [July, 

could  have  been  saved  by  standardization.  Even  though  each  sep- 
arator has  a  regulating-  contrivance  there  are  always  some  condi- 
tions in  practical  operations  which  influence  separation  and  cause 
variation  in  the  richness  of  the  cream.  These  conditions  can  be 
controlled,  to  a  certain  extent,  but  in  order  to  secure  as  little  vari- 
ation as  by  standardizing-  the  operation  will  require  such  vigilance 
and  close  supervision  that  it  would  become  impracticable  for  the 
creamery  man  as  well  as  for  the  dairyman . 

The  first  and  probably  the  most  important  cause  of  these  var- 
iations is  due  to  the  speed  of  the  bowl  in  the  cream  separator  for 
anything-  that  tends  to  chang-e  the  speed  must  necessarily  influence 
the  per  cent,  of  fat  in  the  cream.  Second,  the  temperature  of  the 
milk  has  considerable  influence  on  the  per  cent,  of  fat  in  the  cream. 
A  difference  of  ten  or  more  degrees  in  the  temperature  of  the  milk 
will  cause  a  decided  variation  in  the  per  cent,  of  butter-fat  in  the 
cream.  If  milk  is  warm  the  cream  will  be  thicker,  if  cold  it  will  be 
thinner,  other  conditions  being-  equal.  Third,  the  per  cent,  of  fat 
chang-es  with  the  amount  separated  per  hour.  If  milk  is  fed  into 
a  separator  at  an  uneven  rate  or  if  the  flow  of  milk  is  stopped,  the 
thickness  of  the  cream  will  be  greatly  influenced.  Althoug-h 
cream  separators  are  nearly  all  provided  with  floats  to  reg-ulate  the 
inflow  of  the  milk  into  the  machine,  yet  a  slig-ht  variation  of  press- 
ure as  that  due  to  the  difference  in  the  heig-ht  of  milk  in  the  re- 
ceiving- can  or  tempering-  vat  influences  the  per  cent,  of  fat  in  the 
cream.  Fourth,  the  amount  of  water  or  skim  milk  used  to  flush 
out  the  bowl  at  the  end  of  separation  will  naturally  tend  to  affect 
the  cream  test.  Fifth,  the  condition  of  the  milk  changes  the  per 
cent,  by  having-  small  clots  obstruct  the  cream  or  skim  milk  pass- 
ag-e  in  the  bowl  of  the  separator.  Of  course,  it  is  assumed  that 
milk  or  cream  to  be  standardized  for  direct  consumption  oug-ht  to  be 
in  better  condition,  yet  it  is  not  uncommon  to  find  fresh  milk  in  which 
a  part  of  the  casein  is  in  such  flocculent  masses  that  when  subject 
to  the  pressure  in  the  separator  bowl  they  are  readily  deposited 
on  or  near  the  opening-  of  the  skim  milk  tube  which  slig-htly  ob- 
structs the  opening-  and  tends  to  force  more  skim  milk  out  with  the 
cream,  hence  it  lowers  the  per  cent,  of  fat  in  the  cream.  On  the 
other  hand  a  mass  of  partially  churned  cream  which  will  lodge 
near  and  slig-htly  obstruct  the  cream  opening-  will  produce  an  oppo- 
site effect  by  forcing-  more  skim  milk  out  of  the  skim  milk  opening-, 
thus  increasing-  the  per  cent,  of  fat  in  the  cream.  From  this  it  will 
be  seen  that  it  is  practically  impossible  to  separate  cream  to  such  a 
constant  per  cent,  that  it  is  sufficiently  accurate  to  avoid  testing- 
and  standardizing-. 


1902.]  STANDARDIZATION  OF  MILK  AND  CREAM.  307 

Since  it  is  absolutely  necessary  to  know  the  butter-fat  content 
of  the  milk  to  be  standardized  it  is  essential  to  have  a  Babcock 
tester  which  at  any  rate  should  comprise  a  part  of  the  apparatus 
in  every  dairy. 

The  scales  and  can  or  vat  should  be  so  arranged  that  the  milk 
or  cream  can  be  easily  weighed  and  if  a  vat  is  used  it  should  be 
provided  with  a  cooling-  coil.  It  is  essential  that  milk  be  cooled  as 
soon  as  it  is  milked  or  separated.  Cream  should  also  be  cooled 
after  separating-.  The  cost  of  this  apparatus  for  standardizing-  de- 
pends on  the  amount  of  milk  handled  daily.  For  a  small  dairy  the 
cost  need  not  exceed  16.00. 

SUGGESTIONS. 

While  it  is  true  that  a  slig-ht  variation  in  the  per  cent,  of  but- 
ter-fat in  milk  or  cream  handled  on  a  large  scale  will  more  than 
pay  for  the  extra  labor  in  testing-  the  milk  daily,  yet  on  the  other 
hand  it  does  not  justify  the  outlay  of  money  for  labor  in  testing- 
milk  on  a  small  scale.  This  difficulty,  however,  can  be  overcome 
in  a  manner  which  is  sufficiently  accurate  for  the  average  milk  pro- 
ducer, provided  all  milk  is  to  be  of  one  standard  per  c»nt.  of  but- 
ter-fat. 

As  is  stated  in  Circular  51,  the  quality  of  milk  from  individual 
cows  varies  from  day  to  day,  still  it  is  a  fact  that  the  mixed  milk  of 
a  herd  of  cows  milked  reg-ularly  and  kept  under  uniform  conditions 
will  remain  practically  constant  in  butter-fat  content  during-  a  pe- 
riod of  at  least  three  days  and  unless  a  change  of  cows  takes  place 
in  a  herd  or  the  ration  is  abruptly  changed  it  will  not  be  necessary 
to  test  the  mixed  milk  for  butter-fat  more  than  once  in  three  days, 

Immediately  after  milking  the  weight  of  the  milk  is  taken  and 
it  is  then  poured  into  a  vat  to  be  cooled,  when  all  milk  is  in  the 
vat  it  is  sampled  and  tested  for  butter-fat  content.  The  proper 
standard  can  then  be  reached  by  applying  the  foregoing  methods 
and  rules. 

It  is  quite  necessary  for  large  dairy  companies  to  test  their 
milk  daily  as  slight  variations  in  large  quanities  will  warrant  good 
returns  for  the  extra  effort  in  securing  a  more  uniform  product. 

In  creameries  it  ought  to  be  an  object  to  bring  milk  and  cream 
to  a  desired  standard  in  butter-fat  content  and  on  account  of  the 
extreme  variations  in  the  per  cent,  of  fat  in  milk  brought  to 
creameries  it  is  essential  that  the  output  should  be  tested  daily. 
The  cream  is  weighed  while  separating  and  run  into  a  cooling  vat 
where  it  may  be  standardized. 


308  BULLETIN   NO.    75.  [Jufy, 

Creameries  that  supply  cream  of  different  standards  should  be 
provided  with  several  vats  in  order  to  have  the  run  continuous. 
The  cream  in  each  vat  must  be  weighed  and  tested  to  find  the 
amount  of  butter-fat  before  it  can  be  standardized. 

HOW  TO  OBTAIN  the  COST  OF  CREAM  ON    A  BUTTER-FAT  BASIS. 

It  is  essential  in  dealing-  with  cream  to  know  the  price  for 
which  a  gallon  of  cream  can  be  bought  or  sold  which  will  be 
equivalent  to  the  price  of  the  butter-fat  it  contains  or  the  compar- 
ative price  of  cream  containing  different  per  cents,  of  butter-fat. 

Since  cream  is  usually  sold  by  volume  it  becomes  necessary  to 
know  the  approximate  weight.  Average  milk  weighs  8.6  pounds  a 
gallon  but  as  cream  has  a  wide  range  of  variations  in  the  per  cent, 
of  butter-fat  it  contains,  it  therefore,  varies  in  weight  in  proportion 
to  the  change  in  the  per  cent,  of  fat.  This  is  due  to  the  fact  that  but- 
ter-fat is  the  lightest  constituent  in  milk,  having  a  specific  gravity 
of  .93  while  the  average  specific  gravity  of  milk  is  1.032.  Hence, 
cream  containing  a  low  per  cent,  of  fat  and  much  skim  milk  weighs 
heavier  than  cream  of  a  high  per  cent,  of  fat  which  necessarily 
contains  little  skim  milk,  for  this  reason  the  weight  of  cream  varies 
with  the  per  cent,  of  fat  which  it  contains.  Since  the  difference 
in  weight  is  but  a  trifle,  and  to  avoid  many  standard  weights  in 
commercial  work,  cream  that  ranges  from  18  to  40  per  cent,  is  usually 
put  on  one  basis,  weighing  8.3  pounds  per  gallon.  Any  per  cent, 
below  18  is  estimated  on  the  same  basis  as  milk  ;  i.  e.,  8.6  pounds 
per  gallon  and  any  per  cent,  above  40  is  estimated  at  the  rate  of  8 
pounds  per  gallon. 

THE  PRICE  PER  GALLON  OF  CREAM  EQUIVALENT  TO  THE  PRICE  OF 

B.UTTER-FAT. 

Multiply  the  pounds  of  cream  per  gallon  by  the  per  cent,  of 
butter-fat  in  the  cream,  the  product  will  equal  the  pounds  of  fat 
per  gallon  of  cream. 

Divide  the  number  representing  the  price  per  gallon  of  cream 
by  the  number  of  pounds  of  butter-fat,  the  quotient  will  equal  the 
price  per  pound  of  butter-fat. 

To  illustrate:  What  is  the  price  per  pound  of  butter-fat  if  cream  containing 
20  per  cent,  fat  sells  for  50  cents  per  gallon? 

As  stated  before  a  gallon  of  20  per  cent,  cream  weighs  8.3  pounds. 
8.3X.2O=i.66,  the  pounds  of  butter-fat  in  one  gallon  which  is  worth  50  cents. 
$.5O-M.66=S.3O,  the  price  of  one  pound  of  butter-fat. 

To  FIND  THE  PRICE  PER  GALLON  OF  CREAM  AT  A  CERTAIN  PRICE 

PER  POUND  OF  BUTTER-FAT. 
Multiply  the  pounds  of  cream  per  gallon  by  the  per  cent,  of 


IQO2.]  STANDARDIZATION  OF  MILK  AND  CREAM.  309 

fat  in  the  cream,  the  product  will  be  the  number  of  pounds  of  but- 
ter-fat in  one  gallon  of  cream. 

Multiply  this  product  by  the  price  per  pound  of  butter-fat  you 
desire,  the  product  will  be  the  price  per  g-allon  for  cream. 

To  illustrate:     At  32  cents  per  pound  of  fat  what  would  be  the  price  per  gal- 
lon of  cream  containing  27  per  cent,  butter-fat? 

8. 3X. 27=2.241  pounds  of  fat  in  i  gallon. 

2.241X32  =  71.712,  or  72  cents  the  price  of  the  27  per  cent,  cream. 

To  CALCULATE  THIS  ON  A  BUTTER  BASIS  ^  MUST  BE  ADDED  TO  THE 

BUTTER -FAT. 

To  illustrate:     At  32  cents  per  pound  for  butter  what  price  per  gallon  would 
cream  containing  27  per  cent,  fat  be  worth? 
8.3X. 27  =  2.241,  the  pounds  of  butter-fat, 
1-6  of  2. 24 1 =.373. 
2.24i-f.373=2.6i4 

2.614X32=83.648,  or  83.6  cents   the  price  per  gallon  of  27  per  cent,  cream 
with  butter  worth  32  cents  a  pound. 

HOW  TO  FIND  THE  EQUIVALENT  'PRICE  PER  GALLON  FOR  CREAM 
CONTAINING  DIFFERENT  PER  CENTS.  OF  BUTTER-FAT. 

This  is  best  calculated  on  the  basis  of  proportion. 
Divide  the  means  by  the  extremes. 

To  illustrate:    If  cream  containing  20  per  cent,   butter-fat  is  worth  60  cents 
per  gallon  what  is  cream  worth  containing  25  per  cent,  butter-fat? 
.20  :  .25  :  :  .60  :  x 
6ox. 25  =  15 

15-^.20=75,  or  75  cents,  the  equivalent  worth  of  25  per  cent,  cream  in  com- 
parison to  the  worth  of  20  per  cent,  cream  at  60  cents  a  gallon. 


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